The present invention relates to a deep hole drill, which comprises a cutter head as well as a connecting part integrated with the cutter head which part has a thread, said cutter head being equipped with a chip removing cutting insert, at least one support pad as well as at least one guide bar, the said cutter head has at least one opening for discharging chips, said opening transforming into an inner channel of the cutter head. The two most common systems in deep hole drilling are presently the STS (Single Tube System) system and the Ejector system, the present invention relates to both these systems.
In deep hole drilling, in a workpiece a commonly occurring problem is that the support pads and guide bars, which are arranged on the cutter head, are subjected to the formation of crack, during the deep hole drilling. The reason for this is that the support pads/guide bars are normally made of solid cemented carbide, whereby said support pads/guide bars may be exchangeably fixed on the cutter head or in various ways connected by soldering to the cutter head. During the drilling process, the support pads/guide bars are exposed to high temperatures by the fact that the friction against the hole wall may be high. However, most often the entire support pad/guide bar does not abut against the hole wall, and therefore only a part of said support pad/guide bar is exposed to said friction. The cooling liquid flowing between the cutter head and the bore hole will not be in contact with the support pad/guide bar in those areas where abutment takes place between the support pad/guide bar and the hole wall to a sufficient extent. As a consequence of these interacting circumstances. i.e. high friction and deficient cooling, cracks arise in the support pads/guide bars, which reduce the service life of said support pads/guide bars.
The present invention has as its aim the definition of a deep hole drill of the kind mentioned in the introduction, where the cooling liquid is given a greater possibility to provide cooling of the support pad/guide bar, in an efficient way, during drilling.
Yet another aim of the invention is to improve the chip removal, which reduces the risk for chips being stuck between the support pad/guide bar and the hole wall, which additionally may reduce the service life of said support pads/guide bars.
The aims of the present invention are realized by means of a deep hole drill for chip-removing drilling in a workpiece. The drill comprises a body which includes a cutting head and an integral connecting part adapted for connection to a drill tube. The body forms a longitudinal axis of rotation and has a longitudinal internal channel opening into an end face of the cutting head for receiving cuttings that are entrained in a cooling medium. A chip-removing insert is disposed on the cutting head. A support pad is disposed on a generally cylindrical outer peripheral surface of the cutting head. A guide bar is disposed on the outer peripheral surface in circumferentially spaced relationship to the support pad. A cooling duct is formed in the outer peripheral surface and is oriented generally parallel to the axis at a location adjacent to the support pad. The cooling duct opens at the end face for conducting cooling medium toward the end face. The cooling duct is situated adjacent the support pad for cooling the support pad.